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14 January 2009

Feral cats and the law of unintended consequences

Think eradicating feral cat populations, by killing or relocation, is a good way to save birds? Not on Macquarie Island, it wasn't:

It seemed like a good idea at the time: Remove all the feral cats from a famous Australian island to save the native seabirds.

But the decision to eradicate the felines from Macquarie island allowed the rabbit population to explode and, in turn, destroy much of its fragile vegetation that birds depend on for cover, researchers said Tuesday.

Removing the cats from Macquarie "caused environmental devastation" that will cost authorities 24 million Australian dollars ($16.2 million) to remedy, Dana Bergstrom of the Australian Antarctic Division and her colleagues wrote in the British Ecological Society's Journal of Applied Ecology.

"Our study shows that between 2000 and 2007, there has been widespread ecosystem devastation and decades of conservation effort compromised," Bergstrom said in a statement.

The unintended consequences of the cat-removal project show the dangers of meddling with an ecosystem — even with the best of intentions — without thinking long and hard, the study said.

However, the powers that be don't seem to have drawn that same conclusion. Since the first stage of eradication went so horribly wrong, they've decided to do the same thing only harder and see how that works out:

Several conservation groups including the International Union for Conservation of Nature and Birds Australia said the problem was not the original eradication effort itself — but that it didn't go far enough. They said the project should have taken aim at all the invasive mammals on the island at once.

"What was wrong was that the rabbits were not eradicated at the same time as the cats," University of Auckland Prof. Mick Clout, who also is a member of the Union's invasive species specialist group. "It would have been ideal if the cats and rabbits were eradicated at the same time, or the rabbits first and the cats subsequently."

Liz Wren, a spokeswoman for the Parks and Wildlife Service of Tasmania, said authorities were aware from the beginning that removing the feral cats would increase the rabbit population. But at the time, researchers argued it was worth the risk considering the damage the cats were doing to the seabird populations.

"The alternative was to accept the known and extensive impacts of cats and not do anything for fear of other unknown impacts," Wren said. "Since cats were eradicated, the grey petrel successfully bred on the island for the first time in a century and the recovery of Antarctic prions has continued since the eradication of feral cats."

Now, the parks service has a new plan to finish the job, using technology and poisons that weren't available a decade ago.

Wren said plans to eradicate both rabbits as well as rats and mice from the island will begin in 2010. Helicopters using global positioning systems will drop poisonous bait that targets all three pests. Later, teams will shoot, fumigate and trap the remaining rabbits, she said.

In other words, we must destroy this village to save it.

Of course islands are special ecologies, and I'm not saying that non-native species should be allowed to remain on the island. And I like wild birds, too. But I think we can, and must, do better than a scorched earth eradication program in the name of "ecology," if for no other reason than we're not very good at predicting unintended consequences. And it's worth realizing that by the same logic, we humans should probably get out of almost everywhere we are.

Some sort of physical law that coffee tastes better the farther up the west coast one goes. I keep trying to replicate the effect but it's hopeless. (sigh).

As for non-native species, how about gradual population reduction via selective culling, birth control or relocation (when practical)? That would give an already altered ecosystem a chance to adjust and to demonstrate unintended consequences, which could then be addressed, before they go out of control.

After all, in many of these cases, the invasive species have been present for decades if not centuries.

If it's a recent invasion that has not gotten a foothold, then maybe getting them gone ASAP by more aggressive methods might then be the best choice.

As for feral cats in urban and suburban regions, it's important to note that while they do certainly prey on native species, they also help control other non-native species such as most rats. In suburban areas and rural areas, native and non-native fox of course will do much the same. Since we added cats to our property, the red fox family that was often seen or heard has moved off, I presume because the cats, using the house as home base, have claimed the territory. The cats seem to have a very set hunting territory, usually always close enough to the house for protection, staying well clear of the coyotes and grey fox hangout just to the south and east of or place.

Local AC and Anderson Valley Animal Rescue have instituted a barn cat program to place ferals with rural property owners if they do not have a colony to go to. It's a viable alternative to killing cats if they cannot stay where they are once altered. And it is an alternative also, for ranchers and farmers, to just letting existing cat populations breed to provide the service.

I was a bit surprised when reading this article that only the cats cost to the seabirds was figured in. Surely the rest of the islands ecology must be important? Wholesale rapid eradication using fumigation, poison bait etc... just has more "unintended consequences" written all over it.

I don't know what the answer is, but it's probably not mass destruction. An introduced species changes the balance and becomes part of the ecosystem. We have nutria which undermine the river banks here. They were introduced by someone who was going to start a fur business. Not sure what would happen if they were completely eradicated now. They've been here for a long time. Himalayan Blackberries are an introduced species here, also. They're a noxious weed, and they take over everything, but the ones in my backyard provide very good cover for the birds and are a food source besides. In the coast range they beat out the salal and salmonberries, but leave a much more plentiful food source for the black bears. I've developed a symbiotic relationship with my blackberries. I get pie and jam, they get to live.

Calvin Trillan wrote a great piece for The New Yorker (if I'm remember it all correctly) about Louisiana's efforts to get the great chefs of New Orleans to come up with recipes for nutria as a way to get some demand for the non-native species.

Seriously, though, is there anything worse that kudzu? When I was living near Tallahassee I could not believe how quickly that crap grows. I swear you could see it do so with the naked eye. And out in the backwoods you would see buildings that the vines had pulled apart.

Someone found kudzu in the Portland area a few years back. I think the winters are too cold and wet for it to survive, thank goodness! They cleaned it out as quickly as they could. We have English ivy eradication programs here. It kills everything it grows over and it's incredibly invasive and destructive. Oregon actually has a watchdog program to monitor non-native species. If you see something suspicious, you just report it.